Cameras are used in various scenarios, both indoors and outdoors. Some cameras offer both day and night functionality, such as those designed to be used in outdoor installations or in indoor environments with poor lighting. When in day mode, a camera IR-cut filter filters out IR light such that it does not distort the colors of the images as the human eye sees them, but when the camera is in night mode, the IR-cut filter is removed, thereby allowing the light sensitivity of the camera to reach down to 0.001 lux or lower. Near-infrared light, which spans from 700 nm up to about 1000 nm, is beyond what the human eye can see, but most camera sensors can detect it and make use of it.
Thus, when in day mode, i.e., when the light in the scene is above a certain level, the camera delivers color images. As light diminishes below the certain level, the camera switches to night mode to make use of near infrared, IR, light to deliver high-quality black and white images.
In order to enhance the amount of IR light from a scene viewed by the camera set in night mode, the camera may be equipped with an IR-illuminator configured to illuminate the scene with IR-light. However, depending on the quality of the IR-illuminator and/or the mechanical platform of the camera, an even illumination of the scene might not be possible. A non-even illumination of the scene will affect the quality of the images captured by the camera in night mode. Other factors that might affect the image quality include changes in vignetting of the zoom lens changing due to different levels of zoom. Hence, there is a need for improvement in image quality of images captured with the camera in night mode, in particular when an IR-illuminator is utilized.
One solution to this problem is to specially design the IR-illuminator so that the illumination provided by it is more even. However, such an approach requires vast simulations and testing of the IR-illuminator.